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Biomedical subjects

B Cheng

Publications and source records attributed to B Cheng.

At least 37 records · Page 2Linked to original sources
PubMed2000

[Maintenance of foot sensory function by end-to-side neurorrhaphy].

OBJECTIVE: The purpose of this paper is to introduce the experience in maintaining or reconstructing foot sensory function after harvesting skin flap from the leg. METHODS: After dissecting the fasciacutaneous flap in the medial leg, the end-to-side neurorrhaphy was performed between the distal saphenous nerve and the sural nerve. When the retrograde-flow neurocutaneous island flap was raised, the end-to-side neurorrhaphy was carried out between the sural nerve carried by the flap and the cutaneous nerve of the foot dorsum. Also a less important cutaneous nerve branch can be harvested and implanted into the denervated flap in the foot with the other end of the nerve sutured to the lateral side of the cutaneous nerve of the foot dorsum. RESULTS: This operation was performed on three patients. Postoperative follow-up of 9 to 36 months revealed good results. CONCLUSION: This technique is simple and effective.

Adult↗
PubMed1999

Preparation of Shell-Core Cu(2)O-Cu Nanocomposite Particles and Cu Nanoparticles in a New Microemulsion System.

Shell-core Cu(2)O-Cu nanocomposite particles and metal Cu nanoparticles are synthesized in a new microemulsion system which consists of saturated Cu(2+) salt aqueous solution dispersed in isopropanol and stabilized by polyvinylalcohol (PVA). The size of the composite particles and the thickness of the Cu(2)O shell layer can be controlled by the volume ratio of isopropanol to H(2)O (the ratio is defined as R). When R >/= 1000, it is available to obtain metal Cu nanoparticles. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Recombinant kringle IV-10 modules of human apolipoprotein(a): structure, ligand binding modes, and biological relevance.

The kringle modules of apolipoprotein(a) [apo(a)] of lipoprotein(a) [Lp(a)] are highly homologous with kringle 4 of plasminogen (75-94%) and like the latter are autonomous structural and functional units. Apo(a) contains 14-37 kringle 4 (KIV) repeats distributed into 10 classes (1-10). Lp(a) binds lysine-Sepharose via a lysine binding site (LBS) located in KIV-10 (88% homology with plasminogen K4). However, the W72R substitution that occurs in rhesus monkeys and occasionally in humans leads to impaired lysine binding capacity of KIV-10 and Lp(a). The foregoing has been investigated by determining the structures of KIV-10/M66 (M66 variant) in its unliganded and ligand [epsilon-aminocaproic acid (EACA)] bound modes and the structure of recombinant KIV-10/M66R72 (the W72R mutant). In addition, the EACA liganded structure of a sequence polymorph (M66T in about 42-50% of the human population) was reexamined (KIV-10/T66/EACA). The KIV-10/M66, KIV-10/M66/EACA, and KIV-10/T66/EACA molecular structures are highly isostructural, indicating that the LBS of the kringles is preformed anticipating ligand binding. A displacement of three water molecules from the EACA binding groove and a movement of R35 bringing the guanidinium group close to the carboxylate of EACA to assist R71 in stabilizing the anionic group of the ligand are the only changes accompanying ligand binding. Both EACA structures were in the embedded binding mode utilizing all three binding centers (anionic, hydrophobic, cationic) like plasminogen kringles 1 and 4. The KIV-10/T66/EACA structure determined in this work differs from one previously reported [Mikol, V., Lo Grasso, P. V. and, Boettcher, B. R. (1996) J. Mol. Biol. 256, 751-761], which crystallized in a different crystal system and displayed an unbound binding mode, where only the amino group of EACA interacted with the anionic center of the LBS. The remainder of the ligand extended into solvent perpendicular to the kringle surface, leaving the hydrophobic pocket and the cationic center of the LBS unoccupied. The structure of recombinant KIV-10/M66R72 shows that R72 extends along the ligand binding groove parallel to the expected position of EACA toward the anionic center (D55/D57) and makes a salt bridge with D57. Thus, the R72 side chain mimics ligand binding, and loss of binding ability is the result of steric blockage of the LBS by R72 physically occupying part of the site. The rhesus monkey lysine binding impairment is compared with that of chimpanzee where KIV-10 has been shown to have a D57N mutation instead.

Aminocaproic Acid↗
PubMed1999

Prolonged hypoxic stress increases adrenal cholesterol reserve in rats without causing adrenal hypertrophy.

1. It is known that, in rats, hypoxia stimulates adrenal steroidogenesis, but our understanding of the hypoxic effect on the glandular parameters remains incomplete. 2. Adrenals were collected and analysed from rats that had been exposed to hypoxic conditions for 3 weeks. 3. The results reveal increased adrenal concentrations of corticosterone, free cholesterol and total cholesterol without a change in glandular weight and protein concentration. The increased total cholesterol is primarily associated with enriched cholesteryl adrenate (CE22: 4), cholesteryl arachidonate (CE20: 4) and cholesteryl oleate (CE18: 1).

Adrenal Cortex↗
PubMed1999

Effects of prolonged ACTH-stimulation on adrenocortical accumulation of lipofuscin granules in aged rats.

Subcellular deposition of lipofuscin granules is a marker of aging. Human and rodent adrenal cortices accumulate lipofuscin granules with age, but the mechanism that leads to the accumulation is not known. The ultrastructural appearance of lipofuscin granules resembles that of secondary lysosomes. Since adrenocortical subcellular events are predominantly influenced by ACTH action, we therefore studied the effect of prolonged ACTH-stimulation on adrenocortical accumulation of secondary lysosome-like granules, designated herein as lipofuscin granules. Using aged Fischer 344 male rats as a model, we found that a 7 day ACTH stimulation exerts a reducing effect on adrenocortical lipofuscin accumulation. Thus, adrenocortical accumulation of lipofuscin granules with age in vivo may not be an irreversible process.

Adrenal Cortex↗
PubMed1999

An animal and clinical study on the change of neuropeptide Y release evoked by electrical stimulation and myocardial ischemia.

OBJECTIVE: To investigate the change characteristics of neuropeptide Y (NPY) release during acute myocardial ischemia period. METHODS: The animal test was carried out in in situ perfused guinea pig hearts with intact sympathetic innervation. Electrical stimulation-evoked exocytotic release of NPY during ischemia and reperfusion was tested by radioimmunoassay (RIA). The plasma NPY concentrations were measured in patients with acute myocardial infarction (AMI) and angina pectoris (AP) in different times. RESULTS: Electric stimulation of the left ganglion in guinea pig heart evoked an exocytic release of neuropeptide Y. Stimulation after 20 minutes of global ischemia (S2), compared with control period stimulation (S1) produced the inhibition of NPY to a certain extent (S2/S1: 0.72, P < 0.05), whereas the inhibition of NPY release disappeared after 5 minutes reperfusion (with S2/S1 of 1.01, P > 0.05). Ischemia alone, without the electric stimulation, did not apparently induce NPY release. The clinical test found that the plasma NPY level was increased significantly during the acute ischemia attack period of coronary heart disease (CHD). The plasma NPY level reached peak (136.3 +/- 66.5 pg/ml) in patients during the first day after AMI. It began to decrease from the third day and came to normal level in the end of the first week. The plasma NPY level was 159.3 +/- 98.5 pg/ml in AP patients during angina attack. After two weeks treatment, the plasma NPY level was decreased to 118.9 +/- 54.3 pg/ml (P < 0.05). CONCLUSIONS: The NPY release of global ischemia have some relation with sympathetic nerve activity. At the early stage of ischemia, NPY release is inhibited to some degree and the inhibition factors will fade away on reperfusion. NPY interferes with the pathogenesis and the pathophysiolgy.

Aged↗
PubMed1998

Structure and ligand binding determinants of the recombinant kringle 5 domain of human plasminogen.

The X-ray crystal structure of the recombinant (r) kringle 5 domain of human plasminogen (K5HPg) has been solved by molecular replacement methods using K1HPg as a model and refined at 1.7 A resolution to an R factor of 16.6%. The asymmetric unit of K5HPg is composed of two molecules related by a noncrystallographic 2-fold rotation axis approximately parallel to the z-direction. The lysine binding site (LBS) is defined by the regions His33-Thr37, Pro54-Val58, Pro61-Tyr64, and Leu71-Tyr74 and is occupied in the apo-form by water molecules. A unique feature of the LBS of apo-K5HPg is the substitution by Leu71 for the basic amino acid, arginine, that in other kringle polypeptides forms the donor cationic center for the carboxylate group of omega-amino acid ligands. While wild-type (wt) r-K5HPg interacted weakly with these types of ligands, replacement by site-directed mutagenesis of Leu71 by arginine led to substantially increased affinity of the ligands for the LBS of K5HPg. As a result, binding of omega-amino acids to this mutant kringle (r-K5HPg[L71R]) was restored to levels displayed by the companion much stronger affinity HPg kringles, K1HPg and K4HPg. Correspondingly, alkylamine binding to r-K5HPg[L71R] was considerably attenuated from that shown by wtr-K5HPg. Thus, employing a rational design strategy based on the crystal structure of K5HPg, successful remodeling of the LBS has been accomplished, and has resulted in the conversion of a weak ligand binding kringle to one that possesses an affinity for omega-amino acids that is similar to K1HPg and K4HPg.

Amino Acid Sequence↗
PubMed1998

Effects of prolonged ACTH-stimulation on adrenocortical cholesterol reserve and apolipoprotein E concentration in young and aged Fischer 344 male rats.

Changes in the morphology of rat adrenal cortex with age include increased accumulations of lipid droplets and lipofuscin granules. Because glandular concentrations of cholesteryl esters (CE) and apolipoprotein (apo) E are also increased in parallel, the utilization or metabolism of lipid-droplet stored CE for steroidogenesis might be altered in aging cells. To explore this possibility, adrenocortical cholesterol storage and utilization were studied in 3-6 months-old (mo) (Y) rats and 20-23 mo (O) Fischer 344 male rats. Both groups received either adrenocorticotropin (ACTH1-39, Acthar gel) or gelatin alone daily for seven consecutive days. We found that: (a) the CE concentration in O rats, but not Y animals, was diminished by ACTH. The depleted CE in stimulated-O rats was replenished within five days post stimulation. Failure to deplete CE in stimulated-Y rats was not associated with an insufficient dose of the hormone, since stimulation of Y animals with higher doses of ACTH actually increased the CE concentration. In contrast, adrenocortical free cholesterol concentration remained constant during stimulation regardless of age. (b) The depleted CE in stimulated-O rats was principally comprised of cholesteryl adrenate, cholesteryl arachidonate and cholesteryl cervonate. The accumulated CE in stimulated-Y animals was primarily comprised of cholesteryl adrenate, cholesteryl arachidonate and cholesteryl oleate. (c) Whereas in stimulated-Y rats adrenal apoE concentration declined, the concentration in stimulated O animals was well maintained. (d) In vitro, adrenal homogenate or cytosolic fraction from stimulated-O rats displayed a higher capacity to hydrolyze exogenous CE than its Y counterpart. However, cholesterol esterification with external fatty acid substrates in adrenal homogenate or microsomal fraction was comparable in the two age-groups. Our findings revealed altered adrenocortical cholesterol reserve in O rats to cope with prolonged ACTH-stimulation. Changes in apoE levels and CE hydrolysis activity may be factors associated with this alteration. Depletion and accumulation of adrenocortical CE are reflected in parallel changes in cholesteryl adrenate and cholesteryl arachidonate, suggesting physiologic importance of these polyunsaturated fatty acids during sustained steroidogenesis.

Adrenal Cortex↗
PubMed1998

[Expression of mdr-1 gene in cancer tissue and its association with morphological indexes of esophageal carcinoma].

OBJECTIVE: To detect the levels of mdr-1 gene expression in fresh untreated esophageal carcinomas, and to correlate these levels to current prognostic indicators of morphology. METHODS: mdr-1 gene expression of 46 untreated esophageal carcinoma was investigated with reverse transcription polymerase chain reaction (RT-PCR), and compared with the positive incidences among differentiated grades, TNM stages and macroscopic types of cancer. RESULTS: All 46 samples were pathologically squamous cell carcinoma. The positive incidence of mdr-1 gene expression was 37% (17/46) in the whole group, and 35% (6/17), 40% (8/20), 33% (3/9) for differentiated grade I, II and III respectively. The expression rate of 33% (6/18), 40% (5/12), and 37% (6/16) was for TNM stage IIa, IIb, and III respectively. Macroscopically, the positive incidence was 37% (3/8) in constrictive, 33% (5/15) in fungating, 40% (6/14) in medullary, and 33% (3/9) in ulcerative type. There were no significant differences in each category system of morphology. CONCLUSION: Because of highly expressive level of mdr-1 gene in untreated esophageal carcinoma, we should choose appropriate chemotherapeutic regimen for esophageal Ca. The expression of mdr-1 gene in untreated esophageal cancer was independent of morphologic prognostic indexes without correlation between mdr-1 gene expression and morphological indexes.

ATP Binding Cassette Transporter, Subfamily B↗
PubMed1997

Time course of the effects of a high-fat diet and voluntary exercise on muscle enzyme activity in Long-Evans rats.

This study examined the time course of the effects of a high-fat diet and voluntary running exercise on rat skeletal muscle carnitine acyltransferase (CAT), beta-hydroxy-acyl-CoA dehydrogenase (HAD), and citrate synthase (CS) activities. Sixty male Long-Evans rats were randomly allocated to receive either a standard (12% fat by energy) laboratory chow diet (CHOW) or a high-fat (76% by energy) diet (HFD) and placed in running wheels for up to 6 weeks. Energy intakes and weekly voluntary running distances were similar in the CHOW and HFD rats. In both groups, weekly training distance more than doubled from week 4 to week 6. However, increased training had little influence on soleus (s) CAT(s), HAD(s), and CS(s) activities. CAT(s) and HAD(s) activities were higher in the HFD rats than in the CHOW rats from 2 weeks onward (p < 0.005), and CS(s) activities were not different between groups and remained constant over time. In contrast, increased training distance after 4 weeks in the CHOW rats resulted in an increase in deep vastus (v) CAT(v) activities to values similar to those in HFD rats prior to increases in training volume (p < 0.005) but had no effect on their HAD(v) and CS(v) activities. Increases in HAD(v) and CS(v) activities with increased training volume were only seen in the HFD rats (p < 0.005). HAD(v) activities and HAD/CS(v) activity ratios correlated with training distance in the HFD rats only (p < 0.001 and p < 0.01, respectively). These results suggest that a high-fat diet improves the beta-oxidation capacity of rat predominantly slow-twitch soleus muscle and enhances the effects of modest levels of training on the mitochondrial density and beta-oxidation capacity of rat deep vastus mixed fast- and slow-twitch muscles.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1997

[Mitomycin C concentrations in rabbit ocular tissues after topical administration during glaucoma filtration surgery].

Using high-performance liquid chromatography, we measured Mitomycin C (MMC) concentrations in conjunctiva, sclera and aqueous of 22 rabbit eyes after single topical administration of 0.2 mg.ml-1 MMC during glaucoma filtration surgery. The peaks of MMC concentrations in conjunctiva, sclera, aqueous were 2.01 micrograms.g-1, 2.95 micrograms.g-1 and 0.16 microgram.ml-1 with half life of 0.63, 0.35 and 0.84 hours respectively. Irrigating the ocular surface with 20 ml of normal saline after MMC application reduced the peak drug concentration to 1/8 in conjunctiva, to 1/5 in sclera and to 1/3 in aqueous. The results showed that the MMC concentrations in conjunctiva and sclera were well above the ID50 of rabbit subconjunctival fibroblast (0.1 microgram.ml-1), and the concentration in aqueous was well below the level known to cause endothelium toxicity (approximately 0.2 mg.ml-1) and retinal toxicity (> 1.3 micrograms.ml-1). Therefore, 0.2 mg.ml-1 MMC can inhibit subconjunctival fibroblast effectively and has no side effect on visual function.

Administration, Topical↗
PubMed1996

mu-Oxo-bis[(5,10,15,20-tetraphenylporphyrinato)oxomolybdenum(V)].

The crystal structure of a new solvated crystal form of the title complex, [¿Mo(O)(TPP)¿2O].1.5H2O.0.5CH2Cl2 (TPP = C44H28N4), has been determined. The dimeric molecule is in a general position, and the overall structural features are extremely similar to those of the previously reported non-solvated form.

Crystallography, X-Ray↗
PubMed1996

Chloro(5,10,15,20-tetraphenylporphyrinato)manganese(III) with 4/m symmetry.

The crystal structure of [Mn(TPP)Cl] in space group I4/m (where TPP is C44H28N4) has been determined. The unit cell contains two full molecules, with one eighth of a molecule unique. An out-of-plane model for the Mn atom was applied and all non-H atoms were refined anisotropically. The Mn--N distance is 2.002 (3) A, the axial Mn--Cl distance is 2.297 (15) A and the out-of-plane displacement of the Mn atom is 0.16 A. The possibility of a reverse-doming porphyrin core conformation is mentioned briefly.

Crystallography, X-Ray↗
PubMed1996

A scintigraphic study on gastric emptying in patients with non-ulcer dyspepsia.

Solid gastric emptying rates (GER) were determined with scintigraphic techniques in 20 patients with non-ulcer dyspepsia (NUD) and 9 healthy volunteers. GER were significantly decreased in NUD patients compared with controls, especially 45 min (P < 0.05), 60 and 90 min (P < 0.01) and 120 min (P < 0.05) after ingestion. In 13 out of 20 NUD patients who demonstrated lower GER, only 4 cases gave a lower GER at all stages throughout the determination, the other 9 showed their abnormal GER only after 60 min. In 3 cases who received repeated GER studies after cisapride therapy, 2 patients showed symptomatic relief accompanied by GER improvement. It is concluded that gastric emptying delay may be present with a high percentage in patients with non-ulcer dyspepsia. Scintigraphic gastric emptying test is a safe and reliable technique with good reproducibility. It may be helpful in quantitative study about gastric motion disorders.

Adolescent↗